A number of oil and gas pipelines have been constructed across slopes in the province of Alberta, Canada. They were buried at shallow depths below the sloping surface. Due to complex terrains and geological formations, these slopes are active, continually moving in varying rates. Pipeline sections subjected to such permanent long-term ground deformations may yield because of large strain accumulation over time. It is of practical importance to quantify how such movement rates affect the integrity of the pipe so that an effective field monitoring and remediation program can be developed to maintain the integrity and prolong its operation. This paper develops semi-analytical solutions to estimate the strains exerted on a pipe subjected to varying soil displacement rates. The effects of soil movement rates on the soil-pipe interaction are incorporated into the proposed solutions, which are not considered by the current guidelines for the designs of buried steel pipes (American Lifelines Alliance (ALA 2001) and Pipeline Research Council International (PRCI 2009)). These solutions will be used in a case study to assess the potential of yielding in the pipe with the given soil displacement rates that occurred in the slope. In this particular sloping site, the soil displacement rates of 10 – 50 mm/year were detected over 30 year.

A steel pipe (Grade X52) of 0.6 m in diameter and 5.2 m in length was buried in a rigid soil pit formed by three reinforced concrete walls and a curved masonry wall. The dimensions of the pit are 2.4 m (narrowest width) by 7.6 m (length) by 2.4 m height. The width at two ends of the pit is 3.8 m. The pipe was instrumented with strain gauges mounted externally at two pipe sections to measure both circumferential and longitudinal deformations. The steel pipe was laid at a vertical distance of 1.1 m from the base to minimize the boundary effects. The pipe rested on a layer of loosely compacted sand/gravel with thickness of 200 mm. Silty clay soil was used as backfill material, and compacted in layers. The final burial depth of the pipe is 0.6 m. The mechanical behaviour of the buried pipe was monitored through the compaction. It was observed that the pipe section deflects into a vertical ellipse at the initial compaction up to the pipe top level. This response is then reduced by further compaction of backfill above the pipe as the vertical deformation becomes dominant.

Climate change has the potential to affect substantially the operational condition and lifespan of buried utilities, including pipelines transporting water, gas, and sewer. The climate of Canada is known to vary spatially and temporally, and these variations can cause damage to buried infrastructures. Thus, climate variables can provide useful information related to the failure prediction of water mains. The physical mechanisms that negatively impact the condition of water mains and can lead to their failure are complex and not fully understood. This can lead to high uncertainty in forecasting the possible damage and the need to replace or repair water mains before major failures.
Although climate hazards have become a major concern to cities and municipalities in Canada, only a few studies have addressed the impact of climate variations and forecast their contributions to possible failures of water mains. In this paper, we present a spatiotemporal approach for failure forecasting of water mains at selected locations in the Cities of London (Ontario) and Quebec, Canada. The results show that the proposed model is able to reasonably forecast the failure of water mains up to nine months ahead under climate variations.

Shallow linear infrastructure, like roads, rail and existing pipelines, commonly need to be crossed by new pipeline projects. For these relatively short and shallow crossings, pipelines can usually be installed using a range of available boring methods. Although the value of detailed engineering assessment often conducted for larger scale HDD crossings is not often perceived for these shallow crossings, they are not without risks associated with complex subsurface geology, largely pertaining to intersection of bedrock, coarse granular material or shallow groundwater. Here, we show how a combination of geophysical profiling and test pits can provide a cost-effective means to characterize shallow subsurface geology with minimal ground disturbance. We demonstrate this approach for a series of ten road and pipeline crossings spread over a 23-kilometre-long section of a proposed 42-inch natural gas pipeline in a previously glaciated area of Northeast British Columbia. A combination of seismic refraction and electrical resistivity tomography (ERT) profiles were acquired to non-invasively map the subsurface geology, from which select locations were proposed for targeted test pitting to ground truth results. At crossing locations where the combined investigation results identified potential risk with the preliminary borepath design (e.g., in and out of shallow bedrock), the results were then used to optimize the depth profile, and to select the best-suited crossing configuration, boring method and tooling.